The present invention relates to the magnetic resonance diagnostic arts. It finds particular application in conjunction with the simultaneous imaging of a plurality of human organs and will be described with particular reference thereto. It is to be appreciated, however, that the invention will also find application in conjunction with the concurrent imaging of non-human subjects and in conjunction with certain spectroscopic examinations of human and non-human subjects.
Conventional magnetic resonance imaging systems can perform whole body imaging in which a large region of the torso is examined. Diagnostic images which typically span the large region may intersect adjacent organs. However, the scale or detail associated with individual organs within a small part of the large image are relatively limited. Another disadvantages with whole body RF coils is that the signal-to-noise ratio tends to be low.
To obtain improved, more detailed images of organs, conventional magnetic resonance imaging systems include dedicated transmission and reception coil assemblies for performing diagnostic examinations of a single organ at a time. In many instances, a separate transmitter coil and a receiver coil are used to generate images of the selected organ. Often, the RF coil assemblies are dedicated to a specific part of the human body, such as a head coil or a neck coil. Generally, a dedicated RF coil is only used to produce images from the corresponding organ. The magnetic resonance signal received by the dedicated RF coil itself is sufficient to generate a magnetic resonance image of the corresponding organ.
The dedicated RF coil assemblies can be either a single coil or a combination of RF coils which operate together to generate an image of the region of interest. One type of multiple coil assembly for imaging a dedicated region is a phased-array coil. See for example, U.S. Pat. No. 4,825,162 of Roemer, et al. or U.S. Pat. No. 4,973,907 of Bergman, et al.
Using individual surface coils to image multiple organs has drawbacks. First, the patient must be removed from the bore of the magnetic resonance imager to swap dedicated coils. This reduces patient throughput. Second, the images of the two organs are taken at time displaced intervals. In some diagnostic techniques, it would be advantageous to image two or more organs in a known temporal relationship. For example, it is often advantageous to coordinate images of the heart and images of the patient's circulatory system or other organs whose configuration or functioning changes with the cardiac cycle. Analogously, other pairs of organs can be imaged in a known relationship.
With phased-array RF coils, images of a single organ or a localized volume in the patient are generated with the several linear surface coils of the phased-array. Each coil contributes a part of the whole image. Multiple receiver channels are required with the phased array. Moreover, image data from each phased-array coil is combined with images or signals from other coils of the array and undergo a complicated image processing procedure. To the extent that a phased-array coil might extend adjacent to organs, the coil system is optimized for only a single one of the organs.
In accordance with the present invention, a new and improved imaging method is provided in which two or more organs are imaged concurrently.